I am using this index for presumed nominate Yellow-legged Gull (Larus michahellis), which includes the birds from Gibraltar to Romania, and the new colonies in NW Europe. All birds posted on this page are presumed to be michahellis:

: a series of first-cycle birds from various dates from Catalonia, NE Spain. (Oct - March) - added 03/08/07
: a juvenile (standing, fanned tail) from Baltic Germany (Aug)
: a juvenile (standing) from Baltic Germany (Aug)
: a juvenile (standing) from Baltic Germany (Sep)
: a juvenile/first-basic (standing) from Baltic Germany (Sep)
: a molting juvenile (standing) from France (Sep)
: a first-basic (standing) from Baltic Germany (Oct)
: a first-basic (standing) from Baltic Germany (Nov)
: a first-basic (standing) from England (Jan) - added 01/25/08
: a first-basic (standing) from England (Jan) - added 01/25/08
: a first-basic (flying) from Baltic Germany (Nov)
: a first-basic (flying) from Germany (Sep) - added Apr/02/00
: two first-basics (standing) from Balaeric Spain (Dec) - added 06/19/00
: a 2nd-basic (standing) from central England (March)
: a second-basic (standing) from England (Jan) - added 01/25/08
: an definitive-basic (standing) from Balaeric Spain (Dec) - added 06/19/00
: a definitive-adult (flying) - prob. a wintering michahellis? from Morocco (Feb)
: a definitive-alternate (standing) from NE Spain (May) - added 03/04/02

: A collection of birds from Mediterranean Spain (Nov) - added 11/26/2016